An integrated circuit package typically includes an integrated circuit (IC) mounted on a package substrate. The package substrate may include conductive pathways for routing signals in and out of the integrated circuit. Generally, the package substrate may be formed from a plurality of substrate layers for complex signal routings. Plated through-hole (PTH) vias may be utilized for transmitting signals from one substrate layer to another substrate layer.
Signals that are transmitted through PTH vias are generally susceptible to signal crosstalk interference. Signal crosstalk interference occurs when one signal interferes with another signal. Signal crosstalk interference often occurs when two signal conductors that are transmitting signals are close to each other. Hence, in most package substrates, the distance or “pitch” between two consecutive signal transmitting PTH vias is relatively large. Signal crosstalk interference may be further reduced by surrounding the signal transmitting PTH vias with ground PTH vias (i.e., PTH vias that are coupled to ground).
There are, however, a few drawbacks to having ground PTH vias surrounding a signal transmitting PTH via. One of the drawbacks is the large space requirement on a substrate layer due to the number of ground PTH vias needed. Consequently, the density or the number of signal transmitting PTH vias on a particular substrate layer is significantly reduced. This may lead to an increase in the number of substrate layers needed in a single package substrate. With every new generation of integrated circuit packages, the increase in package size becomes more critical.
It is within this context that the embodiments described herein arise.